This invention relates to magnetic recording media, such as thin film magnetic recording disks, and to a method of manufacturing the media. The invention has particular applicability to high areal density magnetic recording media exhibiting low noise, and high coercivity.
The increasing demands for higher areal recording density impose increasingly greater demands on thin film magnetic recording media in terms of remanent coercivity (Hr), magnetic remanance (Mr), coercivity squareness (S*), medium noise, i.e., signal-to-medium noise ratio (SMNR), and narrow track recording performance. It is extremely difficult to produce a magnetic recording medium satisfying such demanding requirements.
The linear recording density can be increased by increasing the Hr of the magnetic recording medium, and by decreasing the medium noise, as by maintaining very fine magnetically non-coupled grains. Medium noise in thin films is a dominant factor restricting increased recording density of high-density magnetic hard disk drives, and is attributed primarily to inhomogeneous grain size and intergranular exchange coupling. Accordingly, in order to increase linear density, medium noise must be minimized by suitable microstructure control.
It is recognized that the magnetic properties, such as Hr, Mr, S* and SMNR, which are critical to the performance of a magnetic alloy film, depend primarily upon the microstructure of the magnetic layer which, in turn, is influenced by the underlying layers, such as the underlayer. It is also recognized that underlayers having a fine grain structure are highly desirable, particular for growing fine grains of hexagonal close packed (HCP) Co-alloys deposited thereon.
It has been reported that nickel-aluminum (NiAl) films exhibit a grain size that is smaller than similarly deposited Cr films, which are the underlayer of choice in conventional magnetic recording media. Li-Lien Lee et al., xe2x80x9cNiAl Underlayers For CoCrTa Magnetic Thin Films,xe2x80x9d IEEE Transactions an Magnetics, Vol. 30, No. 6, pp. 3951-3953, 1994. Accordingly, NiAl thin films are potential candidates as underlayers for magnetic recording media for high-density longitudinal magnetic recording. However, it was found that the coercivity of a magnetic recording medium comprising an NiAl underlayer is too low for high density recording, e.g., about 2,000 Oersted (Oe) The use of an NiAl underlayer is also disclosed by C. A. Ross et al., xe2x80x9cThe Role Of An NiAl Underlayers In Longitudinal Thin Film Media,xe2x80x9d J. Appl. Phys. 81(a), P.4369, 1997.
In order to increase Hr, magnetic alloys containing platinum (Pt), such as Coxe2x80x94Crxe2x80x94Pt-tantalum (Ta) alloys have been employed. Although Pt enhances film Hr, it was found that Pt also increases media noise. Accordingly, it has become increasingly difficult to achieve high areal recording density while simultaneously achieving high SMNR and high Hr.
In copending U.S. patent application Ser. No. 09/152,326 filed on Sep. 14, 1998, now U.S. Pat. No. 6,117,570 a magnetic recording medium is disclosed comprising a surface oxidized seed layer, e.g., an oxidized NiAl layer, and sequentially deposited thereon a Cr-containing underlayer, a CoCrTa intermediate layer and a CoCrPtTa magnetic layer.
Doerner""s U.S. Pat. No. 5,523,173, entitled xe2x80x9cMagnetic recording medium with a CoPtCrB alloy thin film with a 1120 crystallographic orientation deposited on an underlayer with 100 orientation,xe2x80x9d demonstrated that (11.0) textured CoCrPtB medium has lower noise than CoCrPt medium on Cr-alloy underlayer.
Lee""s U.S. Pat. No. 5,693,426, entitled xe2x80x9cMagnetic recording medium with B2 structured underlayer and a cobalt-based magnetic layer,xe2x80x9d discloses CoCrPtB as an alloy for a magnetic layer. Also, Lee discloses that a (10.0)Co peak was observed in a CoCrPt/NiAl film, in which the NiAl layer was the underlayer and the CoCrPt layer was the magnetic layer. However, Lee does not disclose a (10.0) crystallographic orientation in a B and Co containing magnetic layer.
There exists a need for high areal density magnetic recording media exhibiting high Hr and high SMNR. There also exists a need for magnetic recording media containing a glass or glass ceramic substrate exhibiting high Hr, and high SMNR.
An advantage of this invention is a magnetic recording medium for high areal recording density exhibiting low noise and high Hr.
Another advantage of this invention is a method of manufacturing a magnetic recording medium suitable for high areal recording density and exhibiting low noise and high Hr.
According to one embodiment of this invention, a magnetic recording medium comprises a substrate means for supporting a magnetic recording film and a magnetic recording means for recording data, the magnetic recording means comprising B, Cr and Co, and wherein the magnetic recording means is located on the substrate means and has a substantially (10.0) crystallographic orientation. The substrate means includes any substrate such as a glass, glass-ceramic, NiP/aluminum, metal alloys, plastic/polymer material, ceramic, glass-polymer, composite materials or other non-magnetic materials. The magnetic recording means is a material capable of being magnetized, typically in the form of a magnetic layer.
Additional advantages and features of this invention will be set forth in part in the description that follows and in part will become apparent to those having ordinary skill in the art upon examination of the following description and from the knowledge gained by practicing the invention. The advantages of this invention may be realized and obtained and are particularly pointed out in the claims.
According to this invention, the foregoing and other advantages are achieved by a magnetic recording medium comprising a substrate; an underlayer on the substrate; and a magnetic layer comprising B, Cr and Co. The magnetic layer has a substantially (10.0) crystallographic orientation, which gave certain advantages over a recording medium having a (11.0) crystallographic orientation. This is especially true for glass and glass-ceramic substrates.
Another aspect of this invention is a method of manufacturing a magnetic recording medium, comprising depositing a seed layer on a substrate; depositing an underlayer on the seed layer; and depositing a magnetic layer on the underlayer. The magnetic layer comprises B, Cr and Co and it has a substantially (10.0) crystallographic orientation.
Additional advantages of this invention will become readily apparent to those skilled in this art from the following detailed description, wherein only the preferred embodiments of this invention is shown and described, simply by way of illustration of the best mode contemplated for carrying out this invention. As will be realized, this invention is capable of other and different embodiments, and its details are capable of modifications in various obvious respects, all without departing from this invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.